Many systems use switching regulators to generate regulated voltages for use by other components of the systems. For example, a buck or step-down regulator generates an output voltage VOUT that is lower than its input voltage VIN. A boost or step-up regulator generates an output voltage VOUT that is higher than its input voltage VIN.
Some switching regulators are controlled using constant on-time or constant off-time (COT) techniques. Using conventional COT techniques, one or more switches are turned on or off for a constant amount of time during each switching period, where the switches are used to generate an output signal. COT control techniques can provide various benefits depending on the implementation, such as a fast response time and a constant switching frequency for a fixed load and a fixed input voltage.
Switching regulators that operate in this manner, however, can generate excessive electro-magnetic interference (EMI), which may interfere with other circuits. The EMI can be caused by noise at the switching frequency and at harmonics of the switching frequency. One approach for reducing EMI is to use external filters with the switching regulators. Unfortunately, these filters require additional circuitry, are bulky and increase the size of the regulators, and cause efficiency losses.